1. Field of the Invention
In the fields of medicine and clinical chemistry, many studies and determinations of physiologically reactive species such as cells, proteins, enzymes, cofactors, nucleic acids, substrates, antigens, antibodies, and so forth are carried out using conjugates involving specific binding pair members or labels or the like. Various assay techniques that involve the binding of specific binding pair members are known. These assay techniques generally also involve a label used in the detection part of the assay.
Polysaccharides, particularly dextran, have been conjugated to specific binding pair members to increase the stability of the specific binding pair member. Conjugation of these members to polysaccharides also increases the bulkiness of these molecules, which can enhance their effectiveness in assays involving specific binding pair members by interfering with binding to complementary specific binding pair members. Additionally, these conjugates, when present on a surface, permit specific binding of a complementary specific binding pair member to the surface with greatly reduced non-specific binding.
Aminodextran or carboxymethyldextran have usually been utilized for forming conjugates to specific binding pair members. Coupling the dextran to a protein, for example, can then be carried out through formation of an amide. However, aminodextrans and carboxymethyldextrans have a charge that often must be neutralized to control non-specific binding. Such neutralization is difficult to do without derivitizing the conjugate biomolecule at the same time.
An alternative method of conjugation is to first partially oxidize the polysaccharide with periodate to introduce aldehyde groups. Coupling to amine containing ligands and receptors can then be carried out by reductive amination. Although dextrans that are partially oxidized are not charged, the oxidation is difficult to precisely control, and the products have substantially reduced stability toward hydrolysis. A procedure for introducing aldehyde groups onto polysaccharides that does not compromise stability, is more readily carried out, and that permits ready conjugation is therefore needed.
2. Description of the Related Art
Lauritzen, et al., discuss dot immunobinding and immunoblotting or picogram and nanogram quantities of small peptides on activated nitrocellulose in Journal of Immunological Methods (1990) 131:257-267.
Effective immunoadsorbents based on agarose-polyaldehyde microsphere beads: synthesis and affinity chromatography are disclosed by Margel, et al., Analytical Biochemistry (1983) 128:342-350.
U.S. Pat. No. 4,264,766 (Fischer) discloses immunological diagnostic reagents.
U.S. Pat. No. 4,801,504 (Burdick, et al.) discusses fluorescent labels having a polysaccharide bound to polymeric particles.
Polysaccharide-modified immunoglobulins having reduced immunogenic potential or improved pharmacokinetics is discussed in European Patent No. 0 315 456 B1.
Wang, et al., describe a facile synthesis of an aldehydic analog of platelet activating factor and its use in the production of specific antibodies in Chemistry and Physics of Lipids (1990) 55:265-273.